1. Technical Field of The Invention
This invention relates to a method for the oxidation of polyoxypropylene glycols. More particularly, this invention relates to the method for preparing carboxylic acid derivatives and methyl ketone derivatives of polyoxypropylene glycols. Still more particularly, this invention relates to a method for the controlled selective nitric acid oxidation of a polyoxypropylene glycol in order to selectively provide carboxylic acid derivatives or methyl ketone derivatives thereof.
It has been discovered in accordance with the present invention that when the nitric acid oxidation of a polyoxypropylene glycol is conducted in the presence of an alkali metal nitrite the oxidation can be conducted under acid conditions in order to selectively provide carboxylic acid derivatives or methyl ketone derivatives of the polyoxypropylene glycol.
In accordance with one embodiment of the present invention, the alkali metal nitrite is added to an aqueous solution of nitric acid and the polyoxypropylene glycol is thereafter added in order to provide carboxylic acid derivatives of the polyoxypropylene glycol.
In accordance with another embodiment of the present invention, a mixture of an alkali metal nitrite and a polyoxypropylene glycol is added to an aqueous solution of nitric acid in order to provide a reaction product containing a predominant amount of methyl ketone derivatives of the polyoxypropylene glycol.
2. Prior Art
General information on oxidation with nitric acid and nitrogen oxides is given in Chapter IV by Yoshiro Ogata (pp. 295-317) of the text "Oxidation in Organic Chemistry, Part C," edited by Walter S. Trahanovsky, New York Academic Press, 1978.
Languar et al. U.S. Pat. No. 4,793,905 discloses a method using a transition metal electrocatalyst for the manufacture, for example, of an ester or a carboxylic acid such as ethyl acetate from an alcohol such as ethanol.
The oxidation of polyoxyethylene glycols to the corresponding polyoxyethylene dicarboxylic acids using molecular oxygen and a supported platinum catalyst is disclosed in Morris et al. U.S. Pat. No. 4,256,916.
In U.S. Pat. No. 4,233,460, Willis et al. disclose an extremely mild oxidative process for converting alkoxy alkanols to the corresponding acids with an alkali metal hydroxide and tert.-butyl hydroperoxide in the presence of a catalytic amount of palladium.
U. K. patent application GB 2 152 050 A discloses a process for preparing alkali metal salts of monoalkyl ethers of polyoxyethylene monoalkyl ethers of polyoxyethylene glycols by oxidizing the monoalkyl ether in solution an aqueous alkaline medium with oxygen in the presence of a platinum or palladium catalyst.